This module has three functions to extract data from country data templates (which are used for most flag templates).
Extracts all parameters from a data template and returns them as a Lua table. This function is only usable from other Lua modules; invoke it using require('Module:CountryData').gettable(''parameters'').
The first parameter is the frame of the invoking module; the second is the country or other entity to get the data of. The optional third parameter is a table of parameters to pass into the data template; this may, for example, include or, which are used in the values of some sports alias parameters. E.g.,
The function returns an empty table if a data template does not exist or does not conform to the standard structure.
If used from wikicode, this function returns the value of a single field in a data template. The first parameter is the country or other entity whose data to return; the second is the name of the field. For example, {{((}}#invoke:CountryData|getalias|France|flag alias{{))}} → . The other parameters are to return a variant parameter value, with fallback to the main field value if the variant does not exist, and for the fallback output if the wanted data template or field does not exist, the default for which is a literal "nil".
Note: This is likely not quicker than wikicode-only alternatives such as and, because it transcludes the data template from Lua and converts it to a Lua table using the above function, picks the wanted parameter name, and returns it to wikicode, whereas other templates perform two simple non-Lua transclusions to get, in most cases, the same result. The Lua version does have the advantage that using it with a non-existing country data template returns "nil" (or the value of) rather than a redlink to the data template. See a comparison of the four at User:SiBr4/Flagg tests#Lua-based getalias.
This function concatenates the fields of a data template into a string similar to what you get when transcluding it directly. It can be compared with a direct transclusion to test if a template is being converted to Lua correctly:
{{#tag:pre|{{Country data France}}}}
{{#tag:pre|{{#invoke:CountryData|gettemplate|France}}}}
givesNote that, like with all Lua tables, the order of entries is not preserved, so the parameters are mixed up.